Template-driven approach for generating models on network services

ABSTRACT

A method and system of modeling a selected service within a network environment includes forming a service model template that is not specific to the network environment, but identifies anticipated network elements and network services that cooperate to enable the selected service. The service model template includes specifications related to linking the anticipated network elements and network services. When the service model template is combined with discovered instance information that is specific to actual network elements and actual network services, a service model instance is generated for the selected service. The service model instance includes identifications of dependencies among the elements and services. Preferably, the service model instance also includes identification of the “health” of the different elements and services. A view generator may be used to configure the service model instance as a hierarchical graph of nodes that are linked to identify the dependencies among the nodes. The discovered instance information may be acquired using a discovery template that orchestrates the process. The discovery template may identify auto-discovery modules that are to be used to detect actual network elements and services and may identify dependencies among the modules. A user-configurable discovery engine accesses the discovery template and deploys the modules in order to acquire the discovered instance information.

TECHNICAL FIELD

The invention relates generally to methods and systems for linkingcomponents of a service available via a network to assess the health ofthe service and to diagnose problems associated with the service. Moreparticularly, the invention relates to methods and systems forgenerating a hierarchical structure of a network service.

BACKGROUND ART

Originally, computer networks were designed to have a centralizednetwork topology. In such a topology, a centralized mainframe computeris accessed by users at computer terminals via network connections.Applications and data are stored at the mainframe computer, but may beaccessed by different users. However, a current trend in network designis to provide a topology that enables distributed processing andpeer-to-peer communications. Under this topology, network processingpower is distributed among a number of network sites that communicate ona peer-to-peer level. Often, there are a number of servers within thenetwork and each server is accessible by a number of clients. Eachserver may be dedicated to a particular service, but this is notcritical. Servers may communicate with one another in providing aservice to a client.

Networks vary significantly in scope. A local area network (LAN) islimited to network connectivity among computers that are in closeproximity, typically less than one mile. A metropolitan area network(MAN) provides regional connectivity, such as within a majormetropolitan area. A wide area network (WAN) links computers located indifferent geographical areas, such as the computers of a corporationhaving business campuses in a number of different cities. A global areanetwork (GAN) provides connectivity among computers in various nations.The most popular GAN is the network commonly referred to as theInternet.

The decentralization of computer networks has increased the complexityof tracking network topology. The network components (i.e., “nodes”) maybe linked in any one of a variety of schemes. The nodes may includeservers, hubs, routers, bridges, and the hardware for linking thevarious components. Systems for determining and graphically displayingthe topology of a computer network are known. U.S. Pat. No. 5,276,789 toBesaw et al. and U.S. Pat. No. 5,185,860 to Wu, both of which areassigned to the assignee of the present invention, describe suchsystems. As described in Besaw et al., the system retrieves a list ofnodes and their interconnections from a database which can be manuallybuilt by a network administrator or automatically constructed usingcomputer software. The system can be configured to provide any one ofthree views. An internet view shows nodes and interconnections ofdifferent networks. A network view shows the nodes and interconnectionsof a single network within the internet view. A segment view displaysnodes connected within one segment of one of the networks. Selectednodes on the network, called discovery agents, can convey knowledge ofthe existence of other nodes. The network discovery system queries thesediscovery agents and obtains the information necessary to form agraphical display of the topology. The discovery agents can beperiodically queried to determine if nodes have been added to thenetwork. In a Transmission Controller Protocol/Internet Protocol(TCP/IP) network, the discovery agents are nodes that respond to queriesfor an address translation table which translates Internet Protocol (IP)addresses to physical addresses.

The Besaw et al. and Wu systems operate well for graphically displayinghardware components and hardware connections within a network. From thisinformation, a number of conclusions can be drawn regarding the presentcapabilities and future needs of the network. However, theinterdependencies of the components in providing a particular serviceare not apparent from the graphical display that is presented by thesystem. The complexities of such interdependencies continue to increasein all networks, particularly the Internet.

Another approach is described by J. L. Hellerstein in an articleentitled “A Comparison of Techniques for Diagnosing Performance Problemsin Information Systems: Case Study and Analytic Models,” IBM TechnicalReport, September, 1994. Hellerstein proposes a measurement navigationgraph (MNG) in which network measurements are represented by nodes andthe relationships between the measurements are indicated by directedarcs. The relationships among measurements are used to diagnoseproblems. However, the approach has limitations, since MNGs onlyrepresent relationships among measurements. A user of a system that isbased on this approach must understand the details of the measurements(when, where, and how each measurement is performed) and theirrelationships to the different service elements. This understanding isnot readily available using the MNG approach.

The emergence of a variety of new services, such as World Wide Web (WWW)access, electronic commerce, multimedia conferencing, telecommuting, andvirtual private network services, has contributed to the growinginterest in network-based services. However, the increasing complexityof the services offered by a particular network causes a reduction inthe number of experts having the domain knowledge necessary to diagnoseand fix problems rapidly. Within the Internet, Internet ServiceProviders (ISPs) offer their subscribers a number of complex services.An ISP must handle services that involve multiple complex relationships,not only among their service components (e.g., application servers,hosts, and network links), but also within other services. One exampleis the web service. This service will be described with reference toFIG. 1. Although it may appear to a subscriber of the ISP 10 that theweb service is being exclusively provided by a web application server12, there are various other services and service elements thatcontribute to the web service. For instance, to access the web server12, a Domain Name Service (DNS) server 14 is accessed to provide thesubscriber with the IP address of the web site. The access routeincludes one of the Points of Presence (POP) 16, a hub 18, and a router20. Each POP houses modem banks, telco connections, and terminalservers. A subscriber request is forwarded to and handled by a webserver application. The web page or pages being accessed may be storedon a back-end Network File System (NFS) 22, from which it is deliveredto the web server on demand. When the subscriber perceives a degradationin the Quality of Service (QoS), the problem may be due to any of theweb service components (e.g., the web application server 12, the hostmachine on which the web application server is executing, or the networklinks interconnecting the subscriber to the web server), or may be dueto the other infrastructure services on which the web service depends(e.g., DNS or NFS). The ISP system 10 of FIG. 1 is also shown to includean authentication server 24 for performing a subscriber authenticationservice, a mail server 26 for enabling email service (for login andemail access), and front-end and back-end servers 28, 30 and 32 forallowing Usenet access.

Subscribers demand that ISPs offer reliable, predictable services. Tomeet the expectations of subscribers and to attract new subscribers,ISPs must measure and manage the QoS of their service offerings. Thisrequires a variety of tools that monitor and report on service-levelmetrics, such as availability and performance of the services, and thatprovide health reports on the individual service components.Unfortunately, the majority of management systems have not kept pacewith the service evolution. Available management systems lack thecapability to capture and exploit the inter-relationships that existamong services available in a network environment, such as the Internet.

Each network is unique in various respects, such as the con-figurationof servers, the types of application servers, the service offerings, theorganizational topology, and the inter-service dependencies. Therefore,in order to accurately understand the operations of the network,specific models must be crafted for the services provided within thenetwork. Regarding an ISP system, handcrafting models of servicesavailable via the ISP requires an enormous effort on the part of a humanexpert or group of experts. Consequently, inter-service dependencies aretypically not fully recognized, even by the experts.

What is needed is a method that facilitates construction of a model of acore service available via the network, including inter-servicedependencies that are relevant to providing the core service.

SUMMARY OF THE INVENTION

A method and system for modeling a selected service that is availablevia a network includes utilizing a service model template as a basis forgenerating a service model instance of the selected service. The servicemodel template anticipates -network elements and network services thatcooperate in execution of the selected service. The service modeltemplate is specific to the service, but is independent of anyparticular computing environment. When the template is combined withdiscovery information that is specific to the actual network elementsand the actual network services of a particular computing environment,the service model instance is generated. That is, the service modelinstance is the realization of the template for a particular set ofelements, services and inter-dependencies in a specific computingenvironment.

The discovered instance information that is specific to the actualnetwork elements and actual network services may be acquired using anyof a variety of techniques. However, in the preferred embodiment, thediscovered instance information is determined using auto-discoverytechniques without requiring human involvement. Moreover, the step ofgenerating the service model instance is preferably executed incomputing programming and includes accessing at least one memory storein which the service model template and the discovered instanceinformation are stored.

Also in the preferred embodiment, the service model template includesassociations between measurable performance parameters (e.g.,availability and delay) and the network elements and network services.The step of generating the service model instance may then includeindicating states of various network elements and network services basedon the measurements, with the states being indicative of the “healths”of the elements and services. Once generated, a service model instancecan be used to support management functions, such as operationalmonitoring, capacity planning, customer support, and service-levelcontact management.

While not critical, the method may be utilized to model a serviceprovided by an Intranet or Internet Service Provider (ISP). The servicemodel template may be formed to be substantially generic to ISPs, butthe service model instance will be specific to the ISP of interest.Depending on the service being modeled and the network elements that areanticipated to be involved, the service model template defines nodes ofvarious element types (e.g., hosts, servers, network links and services)and their associated measurements. Moreover, the template indicates thedependencies among the nodes, such as the dependency of the selectedservice on other services (e.g., the Read Mail service depends on theauthentication and NFS services). The template preferably also includesdefault state computation rules for specific nodes, so that the state ofa particular node can be based upon measurements associated with thenode and upon states of dependencies of the node. In the embodiment inwhich the discovered instance information is acquired usingauto-discovery, the process includes a discovery template. The discoverytemplate identifies particular discovery modules that are invoked todiscover elements and services of designated types. The discoverytemplate also identifies each dependency of a discovery module on otherdiscovery modules. Thus, the discovery template is used to orchestratethe process of detecting the network elements and network services thatare relevant to the selected service. The discovery template may also beused to format the outputs of the discovery modules.

The system for modeling the selected service includes memory for storingthe service model template, a discovery engine for initiating operationsspecific to identifying the relevant network elements and services, anda model creation engine that maps the discovered network elements andservices into a framework identified in the service model template.Preferably, the system includes a view generator that provides agraphical display of the service model instance. The display may be ahierarchical graph of nodes that are inter-linked to indicateinter-dependencies among the nodes. Color coding or other schemes may beused to identify the states of the nodes. The view generator isconfigurable to enable different views, so that personnel havingdifferent domains of interest may focus upon different aspects of theservice model instance.

An advantage of the invention is that a service model instance that istailored to a particular computing environment is generated withoutrequiring complete handcrafting by a highly skilled individual. Thecustomization accounts for differences in the number of servicesinvolved in providing a service, geographical locations of services,differences in inter-service dependencies, etc. The use of a servicemodel template renders it easier to modify an existing service modelinstance. By editing the service model template, an ISP can add a newelement type service model instance and cause changes to the attributesof all nodes in the service model instance that represent a specificelement. Without a service model template, such changes would bedifficult to incorporate and may even require extensive changes to thesoftware that generates a service model instance. Moreover, the task ofcorrelating measurements to deduce root-causes of problems has beensimplified. The service model instance encapsulates the knowledge of ahuman expert by reflecting the dependencies that may exist amongservices and among network elements. Thus, the service model instancerepresents the structure of the selected service. By traversing theservice model using logic to interpret the state of the differentservices and elements represented in the model, the root-cause of aproblem is easily identified.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary prior art Internet ServiceProvider (ISP) system.

FIG. 2 is a block diagram of components of a system for modeling aselected service available via a network, such as the ISP of FIG. 1.

FIG. 3 is a block diagram of a management system having components ofFIG. 2.

FIG. 4 is an exemplary layout of components for utilizing the Read Mailservice of the ISP of FIG. 1.

FIG. 5 is a graph of nodes of a Read Mail service model configured usingthe system of FIG. 2.

FIG. 6 is an alternative Read Mail service model graph.

FIG. 7 is a schematic view of first phase internal discovery processingusing the system of FIG. 2.

FIG. 8 is a schematic view of second phase external discovery processingusing the system of FIG. 2.

FIG. 9 is a process flow of steps of the first phase discovery of FIG.7.

FIG. 10 is a process flow of steps of the second phase discovery of FIG.8.

FIG. 11 is a block diagram of the operation of the discovery engine ofFIG. 3.

FIG. 12 is a block diagram of the discovery engine of FIG. 11.

BEST MODE FOR CARRYING OUT THE INVENTION

An overview of a template-driven process for generating a service modelfor a particular network is illustrated in FIG. 2. While the inventionwill be described primarily with reference to application to an ISPsystem, the process has other applications. That is, the process may beused to provide a service model for other providers of services innetwork environments (e.g., for services within a corporation'snetwork).

A first phase in constructing a service model is the generation of aspecification of a service model template 34. The service model templateis a generic specification of the service topology and measurementtopology for the service of interest (e.g., Read Mail service).Depending on the service being modeled and the service elements that arelikely to be involved, the template defines nodes of various types(e.g., hosts, servers, network links, and services) and their associatedmeasurements. Moreover, the template indicates the dependencies amongthe nodes, such as the dependency of the service on other services(e.g., the Read Mail service which refers to a subscriber accessinghis/her mailbox depends on the authentication and NFS services). In thepreferred embodiment, the template also includes default statecomputation rules for specified nodes, so that the state (i.e.,“health”) of a node can be computed based upon measurements associatedwith the node and upon states of dependencies of the node.

The service model template 34 is not specific to any ISP system in thesense that it does not specifically reference any hosts, servers,network links, service groups, or other services or service elements inthe ISP system. The template may be considered as a “lifeless tree.”There is no association between nodes in the service model template andrunning elements, such as hosts and servers. However, the informationcontained in the service template for a node may include the elementtype, the element dependencies, the measurement definitions (e.g., agentto run, the format of the run string, the number and type of parameters,and the format of the output), default state computation rules, defaultthresholds, default baselines, and default alarm generation andcorrelation rules.

In database terminology, the service model template 34 is the schema. Onthe other hand, an instance defines the records in the database and thevalues of the static information. In FIG. 2, the instance 36 isdetermined using auto-discovery, as will be explained fully below.Information regarding the services and service elements (e.g., servers,hosts and links) that exist in the ISP system or other service providersystems may be auto-discovered. The store representing auto-discoveredinformation shall be referred to as the auto-discovered instance 36. Inone embodiment, the auto-discovery approach is dividable into twophases. In the first phase, the information that is available in thedomain name system of an ISP is used to discover the existence and therelationships among different services. In order to allow subscribers toaccess a host using its host name, rather than requiring specificationof an IP address that is more difficult to remember, DNS is used to mapthe host names to the IP addresses for all hosts in the ISP system.Moreover, the exchange of email messages across hosts also occurs usingthe mail exchange records (MX records) maintained by the DNS. Insummary, the domain name system stores a wealth of information that isused in the first phase of the auto-discovery process to discoverInternet services and relationships among them. However, othermechanisms are used in this first phase to supplement the informationacquired from the domain name system.

A second phase of the auto-discovery process uses software agents thatare executed within the ISP system and that take an internal viewpointof the ISP system. Whereas the first phase of discovery identifies mostof the execution, component and organization dependencies, as well assome of the inter-service dependencies, the internal discovery of thesecond phase is focused on determining the inter-service dependencies.The definitions of these dependencies will be set forth immediatelybelow. There are two basic approaches to the internal discovery of thesecond phase. One approach is the use of network probes, which areimplemented in software and are installed at strategic locations on thenetwork to acquire information from headers of packet transmissions. Byprocessing the headers of packets, a software probe can deduce many ofthe relationships that exist among servers. The second basic approach isto use special-purpose discovery agents that are installed on the ISPhosts to discover relationships among services. Rather than examiningheaders of packet transmissions, the special-purpose agents use a numberof operating systems and application-specific mechanisms (such asprocessing service configuration information and application-independentmonitoring tools) to discover inter-service dependencies before formingthe auto-discovered instance 36 of FIG. 2.

As noted immediately above, there are a number of interdependencies ofconcern to forming the auto-discovered instance 36. Theseinter-dependencies include execution dependencies, componentdependencies, inter-service dependencies, and organizationaldependencies. An execution dependency relates directly to an applicationserver process being executed on a host machine. The types ofapplication servers that are executed on host machines include web,email, news, DNS, and NFS. A component dependency occurs in order toensure scalability and redundancy of a service. For example, a webservice may be provided collectively by a number of “front-end servers”(FESs), with round-robin DNS scheduling being used to providesubscribers with a domain name that maps to one of the FESs. ISPs oftenreplicate web, email, and News content across a number of servers. Theround-robin scheduling balances the load among the servers. The serversare grouped together and assigned a single domain name in the DNSdatabase. When the DNS server receives a request for the domain name,the IP address of one of the servers is acquired in the round-robinscheme.

An inter-service dependency occurs when one service accesses anotherservice for its proper operation. For example, a web service depends ona DNS service to allow the subscriber to connect the web server hostusing its IP address, and an NFS service is used to access the webcontent. As another example, a Read Mail service depends on anauthentication service to verify the identity of the subscriber, uses aDNS service to log the subscriber's IP address, and uses an NFS serviceto access the mail content.

Finally, an organizational dependency occurs when there are differentISP operations personnel (e.g., subject matter experts) who areresponsible for different services and service components. For example,an ISP may have a first supervisor managing the web service, a secondsupervisor managing DNS, and a third supervisor managing NFS.Operational responsibilities may also be delegated based upon thegeographical location of the service components. Since the preciseorganizational structure may vary from one ISP to another, theauto-discovery mechanism provides a means by which it can be quicklycustomized for a particular ISP system in order to generate theauto-discovered instance 36 of FIG. 2.

The service model creation engine 38 of FIG. 2 is used to generate aservice model instance 40 based on the service model template 34 andauto-discovered instance 36. Ideally, all of the discovered informationis available prior to instantiation. However, in many cases, discoveryhas to be performed in multiple phases, such as the two outlined above.In such cases, instantiation may occur partially after each phase ofdiscovery. The main advantage of providing a partial service modelinstance is that the partially completed service model can provide aguide to identify the additional information needed in subsequent phasesof discovery. Since new elements and services may be added to the ISPsystem over time, the service model instantiation process has to berepeated periodically to augment the initially created service modelinstance.

Unlike the service model template 34, the service model instance 40 isspecific to an, ISP system. The process of constructing the servicemodel instance using the service model template and the auto-discoveredinstance 36 is referred to as the “instantiation” of the service model.As previously noted, the relationship between the service model templateand the auto-discovered instance is analogous to the relationshipbetween the schema and records in a database.

The service model instance 40 maps services and service elements thatexist in a particular ISP system with nodes in the service modeltemplate. In doing so, the service model instance also specifies a setof measurements that must be made against each of the services andservice elements in the specific ISP system.

The service model instance 40 may be used by a view generator 42. In thepreferred embodiment, the service model instance is represented as agraph of the nodes and edges that identify dependencies of the nodes.Different management functions of an ISP will benefit from viewingdifferent subsets of nodes and edges of the service model instance 40.Thus, the view generator 42 may be used by operations personnel toprovide an “operations view” of only the services and service elementsthat fall in a particular domain of control of the personnel. On theother hand, a “customer support view” may provide an end-to-end view forthe customer support personnel of the ISP. A “planning view” may be usedto graphically present information about usage and performance trends,so that future requirements can be ascertained.

Even when different management functions are interested in the samesubset of nodes and edges of the service model instance 40, there may bedifferent interests with regard to rules to be used for statecomputations. For instances, a management application that visuallydepicts a color-coded hierarchical representation of the service modelinstance to operations personnel may require that hierarchical statepropagation rules be employed in the service model instance. In thismanner, viewing the state of the top-level nodes of the service model,an ISP operator can determine whether any problem has been detected inthe ISP system. In contrast, an application that is responsible forautomatically detecting, diagnosing and reporting the root-causes ofproblems in the ISP system may prefer not to use a hierarchical statepropagation rule, since it is interested in the state of each node of Atthe service model independently of the state of other nodes.

The view generator 42 may be used to define the subset of nodes of aservice model instance that are of interest to a management application,as well as the method for evaluating the states of the nodes ofinterest. The measurements that are associated with the nodes in theservice model instance are common across the different views. However,the rules that apply to computing the state of a particular node basedupon relevant measurements and the states of dependent nodes may bedifferent for the different views. The view generator 42 may expose agraphical user interface that a user can employ to customize the viewsprovided to the user.

A measurement agent configurator 44 may be used to extract informationfrom the service model instance 40, when the information is relevant toscheduling tests and retrieving test results. At the completion of theservice model instance 40, static configuration information as to howthe tests of various elements are to be run may be merged with defaultalgorithm descriptions into a service model instance file. Statecomputation rules, thresholds and alarm correlation rules defaults maybe overridden using the measurement agent configurator. Specificmeasurements may be enabled or disabled. A final measurement agentspecification 46 is generated by the configurator for the specific ISP.The measurements that are identified in the specification 46 areexecuted using software agents 45. The results of the measurements areanalyzed and used by a service model manager 47 to compute the states ofdifferent nodes in the service model.

Overview of Instantiation

FIG. 3 represents an overview of the process for generating thediscovered instance that is used to form the service model instance 40of FIG. 2. As previously noted, a requirement of the instantiation isthe generation of the service model template for the particular serviceof interest. The template may be handcrafted, preferably by a domainexpert of the service. The template includes a specification of theelements involved in providing the service, such as servers and networklinks, and the dependencies of the service on other services, such asthe dependency of Read Mail service on the authentication and NFSservices. As will be explained more fully below, the discovery processincludes designation of a discovery template 48. The discovery templatespecifies the types of services and the service elements to bediscovered. The discovery template also includes specifications ofdiscovery modules 50, 52 and 54 to be invoked in the discovery of thespecified services and service elements.

The service model template 34, the discovery template 48, and thediscovery modules 50, 52 and 54 are utilized within a management system56 for forming the service model instance 40. Another component of themanagement system is a discovery engine 58 that processes informationcontained within the discovery template 48. The discovery engine invokesthe appropriate discovery modules 50-54, interprets the outputs of theinvoked modules, and stores the outputs in memory (or in a database) asthe discovered instance 36, which is made accessible to the servicemodel creation engine 38. The discovery engine 58 supports aconfiguration interface 60 that allows ISP operations personnel tocontrol and customize the discovery process. Through the configurationinterface 60, an ISP operator can restrict the discovery to specified IPaddress ranges on host name patterns. Furthermore, the operator canspecify naming conventions used by the ISP (e.g., for naming terminalservers and POP sites), which are used by some of the discovery modules50-54.

The configuration interface 60 serves as a way for an ISP operator toquickly customize the service model instance 40 that is generated by theprocess. Using the configuration interface, the operator can alsospecify categorization criteria for services and service elements. Forinstance, all the mail services could fall in one category, while theDNS servers could fall in another. The categories assigned to servicesand service elements can represent the organizational structure of theISP, the geographical location of the servers offering the services(e.g., servers in San Francisco fall in one category, while servers inNew York fall in another), or differences in business functions of theservice (e.g., web servers that an ISP is hosting on behalf of businesscustomers, as opposed to local web servers that the ISP offers forproviding access to the dial-up subscribers).

In the preferred embodiment, the configuration interface 60 isimplemented using a graphical user interface (GUI) at an operatorcomputing station. An example of a configuration specification that isentered using the interface 60 is shown in Table 1.

TABLE 1 Hosts   exclude ip   10.1.204.1-10.1.205.1 # exclude all hostswith IP addresses in this range. These hosts represent subscriber#  home PCs WebServers  category name *.com.fakeisp.net WebHost #servers with names of the form *.com.fakeisp.net are Web hosting serversTerminalServers extract name max[0-9]{3}<PopSite> [0-9]t.fakeisp.net#Terminal servers must match the naming pattern above. Extract the POPsite name #   from the terminal server's name

The discovery modules 50-54 obtain the configuration criteria from thediscovery engine 58. The modules execute the appropriate discoverytechniques, and as part of their outputs, record the categories to whichthe different services and service elements belong. The categoryinformation is stored at the discovery instance 36 and is interpreted bythe service model creation engine 38 in a manner that is reflective ofthe service model template 34.

The following sections provide details regarding implementation of theprocess described with reference to FIGS. 2 and 3. Since the servicemodels template 34 depends on the syntax specified in the discoverytemplate 48, the discovery template specification is considered first.All the templates and instances presented as examples use the INI fileformat that is commonly used to represent the content of system files inMicrosoft Windows-based personal computer systems. However, the processmay be implemented using other specification and schema definitiontechnologies (e.g., the Common Information Model specified by theDesktop Management Task Force). Per the INI format, a template or aninstance is organized as different sections, each of which is specifiedby a unique stream enclosed within a pair of square brackets (“[<sectionname>]”).

Discovery Template Specification

A portion of an example discovery template specification is shown inTable 2. Four sections are shown, with each section defining thediscovery template for a specific service or service element. The foursections represent templates for discovery of external name servers,hosts, Mail SMTP servers, and Mail POP3 servers. The “module” variablespecification in each section identifies the discovery module 50-54 ofFIG. 3 that is to be used for the particular service or service element.The “arguments” variable represents arguments that are to be passed bythe discovery engine 58 to the discovery module during deployment. The“outputs” variable defines the number and names of the columns in theoutput of the discovery module. The “instanceKey” variable denotes theindex that is to be used to access the discovery instance 36corresponding to each row of output generated by the discovery module.The name or names specified within angled brackets (< >) on the rightside of the instancekey assignment must correspond to one of the columnnames specified in the output assignment. Finally, the “dependencies”variable indicates the dependencies that a discovery module has on othermodules. The discovery engine uses this information to select a sequencein which it processes the discovery templates.

TABLE 2 [ExternalNameServers]discovery-module=DiscoverExternalNameServers.classdiscovery-arguments=-url http://ism-pc2/scripts/discEngineAPI.pldiscovery-outputs=ipAddress, hostName, domainName, categorydiscovery-instanceKey=<ipAddress>:DNS discovery-dependencies= [Hosts]discovery-module=DiscoverHosts.class discovery-arguments=-urlhttp://ism-pc2/scripts/discEngineAPI.pl discovery-outputs=ipAddress,hostName, state, category discovery-instanceKey=<ipAddress>:Hostdiscovery-dependencies=ExternalNameServers [SMTPServers]discovery-module=DiscoverSmtpServers.class discovery-arguments=-urlhttp://ism-pc2/scripts/discEngineAPI.pl discovery-outputs=ipAddress,hostName, category discovery-instanceKey=<ipAddress>:Smtp_Maildiscovery-dependencies=Hosts,ExternalNameServers [POP3Servers]discovery-module=DiscoverPop3Servers.class discovery-arguments=-urlhttp://ism-pc2/scripts/discEngineAPI.pl discovery-outputs=ipAddress,hostName, relatedSmtpServer, categorydiscovery-instanceKey=<ipAddress>:Pop3_Maildiscovery-dependencies=Hosts,ExternalNameServers

There are other possible template processing policies that a discoveryengine can adopt. For example, if the sections in the discovery templateare ordered to reflect the dependencies among sections (e.g., a sectionappears in the template only after appearance of all sections on whichit depends), the discovery engine 58 can proceed to process the sectionsof the discovery template in order. Another possibility is that theorder of processing the sections in the discovery template may bedetermined based on the order in which sections in the service modeltemplate are processed. As will be explained below, sections in theservice model template 34 have references to sections in the discoverytemplate 48.

Discovered Instance Specification

Table 3 is a portion of an example of the discovered instance 36 of FIG.3. Section names in the discovered instance correspond to theinstanceKey variable specifications and the discovery template of Table2. For each of the output variables in the discovery template, there isan assignment in the discovered instance of Table 3. The ISP systembeing discovered in this example is assumed to have the domain namefakeisp.net.

TABLE 3 [10.174.173.23:DNS] ipAddress=10.174.173.23hostName=dns1.fakeisp.net domainName=fakeisp.netcategory=ExternalDnsServer [10.174.173.23:Host] ipAddress=10.174.173.23hostName=dns1.fakeisp.net state=Alive category= [10.137.196.52:Host]ipAddress=10.137.196.52 hostName=mailfes21.fakeisp.net:smtp.fakeisp.netstate=Alive category= [10.137.196.54:Host] ipAddress=10.137.196.54hostName=mailfes22.fakeisp.net state=Alive category=[10.137.196.56:Host] ipAddress=10.137.196.56hostName=mailfes23,fakeisp.net state=Alive category=[10.137.196.58:Host] ipAddress=10.137.196.58 hostName=www.fakeisp.netstate=Alive category= [10.137.196.69:Host] ipAddress=10.137.196.69hostName=www.xyz.com.fakeisp.net state=Alive category=[10.137.196.70:Host] ipAddress=10.137.196.70hostName=www.abc.com.fakeisp.net state=Alive category=[10.137.196.52:Smtp_Mail] ipAddress=10.137.196.52hostName=mailfes21.fakeisp.net:smtp.fakeisp.netcategory=ExternalSmtpServer [10.137.196.52:Pop3_Mail]ipAddress=10.137.196.52 hostName=mailfes21.fakeisp.netrelatedSmtpServer=smtp.fakeisp.net category= [10.137.196.54:Pop3_Mail]ipAddress=10.17.196.54 hostName=mailfes22.fakeisp.netrelatedSmtpServer=smtp.fakeisp.net category= [10.137.196.56:Pop3_Mail]ipAddress=10.137.196.56 hostName=mailfes23.fakeisp.netrelatedSmtpServer=smtp.fakeisp.net category=

Next, a portion of a service model template specification is presentedin Table 4 as an example service model template 34. The service modeltemplate contains the intelligence to map the discovered instance intothe service model nodes. The discovery modules (and hence the discoveredinstance) are designed independently of the service model instance beinggenerated. This enables the same discovered instance to be used in thegeneration of different service models (e.g., for different services).Each section in the service model template represents a type of node inthe service model instance 40 and contains a series of instructions forcreating a node in the service model instance. The service modelcreation engine 38 processes sections of the service model template, oneat a time, attempting to match the template with elements in thediscovered instance 36. Each element in the discovered instancecorresponds to a section of the discovered instance specification. Linesbeginning with a “;” represent comments. These lines are ignored by theservice model creation engine 38 when it processes the service modeltemplate.

TABLE 4 [SM-Host] ; Host Node in the service model match=[*:Host] ; foreach discovered Host instanceKey=<ipAddress>:SM-Hostmeasurements=TCP-Connection Rate(<ipAddress>), VMstat(<ipAddress>),IFstat(<ipAddress>) ; these are measurements of the host ; next copy itsattributes to the SM node hostname=<hostName> ipAddress=<ipAddress>state=<state> category=<category> [SM-Web] ; SM node for a web servermatch=[*:Web] ; match all discovered Web server instancesinstanceKey=<ipAddress>:SM-Webcomponents=<ipAddress>:SM-Host,<ipAddress>-msIP:SM-Linkmeasurements=HTTP-TCPConnectionTime(<ipAddress>) ; next copy all theattributes from the server discovered instancestateComputationRule=measurementsOnly serverType=<serverType>hostName=<hostName> ipAddress=<ipAddress>category=append(<category>,<ipAdress>:SM-Host?<category>)[SM-WebService] ; a web service node match=[*:SM-Web] ; there is a webservice node corresponding to each web server nodeinstanceKey=<ipAddress>:SM-WebServcie measurements=HTTP-Availability(<ipAddress>), HTTP-TotalResponseTime(<ipAddress>), HTTP-DnsTime(<ipAddress>) components=<ipAddress>:SM-Web, <<ipAddress>,Web>:SM-NFS,<<ipAddress>, Web>:SM-DNS ; NFS and DNS service dependencies will bedetermined by phase 2 discovery category=<category> [SM-WebServiceGroup]match=[*:WebServiceGroup]instanceKey=<serviceGrpName>:SM-WebServiceGroupcomponents=list(<serviceGrpComponentsList>) :SM-WebServicecategory=<category>category=append(list(<serviceGrpComponentsList>):SM-WebService?<category>)[SM-TopLevel-Web] instanceKey=Web:SM-TopLevelWebcomponents=*:SM-WebService, *:SM-WebServiceGroup ; components are allweb services and all web service groups [SM-DNS] match=[*:DNS]instanceKey=<ipAddress>:SM-DNS components=<ipAddress>-msIP:SM-Linkmeasurements=DNS-Availability(<ipAddress>),DNS-CacheHitResponseTime(<ipAddress>)stateComputationRule=measurementsOnly ipAddress=<ipAddress>hostName=<hostName> domainName=<domainName> category=<category> [SM-NFS]match=[*:NFS] instanceKey=<ipAddress>:SM-NFScomponents=<ipAddress>:SM-Host measurements=NFS-TotalCalls(<ipAddress>),NFS-DupReqs(<ipAddress>), NFS-TimeoutPercent(<ipAddress>)stateComputationRule=measurementsOnly ipAddress=<ipAddress>hostName=<hostName> [SM-Pop3_Mail] match=[*:Pop3_Mail]instanceKey=<ipAddress>:SM-POP3_Mail components=<ipAddress>:SM-Hostmeasurements=POP3-TCPConnectionTime(<ipAddress>) hostName=<hostName>category=<category> relatedSmtpServer=<relatedSmtpServer>ipAddress=<ipAddress> [SM-ReadMailService] match=[*:SM-Pop3_Mail]instanceKey=<ipAddress>:SM-ReadMailServicemeasurements=POP3-Availability (<ipAddress>),POP3-TotalResponseTime(<ipAddress>), POP3-AuthenticationTime(<ipAddress>) stateComputationRule=defaultcomponents=<ipAddress>SM-Pop3_Mail, <<ipAddress>,Pop3_Mail SM-NFS>,<<ipAddress>,Pop3_Mail:SM-Auth> category=<category>[SM-ReadMailServiceGroup> match=[*:Pop3MailServiceGroup]instanceKey=<serviceGrpName>:SM-ReadMailServiceGroupcomponents=list(<serviceGrpComponentsList>):SM-ReadMailServicecategory=<category> [SM-TopLevel-ReadMail]instanceKey=ReadMail:SM-TopLevel-ReadMailcomponents=*:SM-ReadMailService, *:SM-ReadMailServiceGroup [SM-Category]match=[*;Category] instanceKey=<categoryName>:SM-Categorycomponents=*SM-*?category=<categoryName>

Most sections of the service model template 34 begin with a “match”criteria. The match criteria for a section of the service model templatespecifies the discovery instances that are relevant to the section underconsideration. For instance, the match criteria corresponding to thehost node's specification (SM-Host) in the discovery template indicatesthat the corresponding discovered instances are those of type Host. Thematch criteria is specified as a regular expression that is matchedagainst section names (instance keys) of the discovered instance 36. Foreach object (section) in the discovered instance that matches theregular expression specified in the match criteria, a corresponding nodeis instantiated in the service model instance 40.

Each section of the service model template 34 can match discoveredinstances of at least one type. When a discovered instance satisfies thematch criteria specified in a section of the service model template 34,any of the attributes of the discovered instance can be referred to inthe subsequent instructions of the service model template's section. Theabsence of a match criteria in the specification of a section of theservice model template indicates that there is only one instance of thattype for the particular ISP.

The instanceKey variable in Table 4 denotes the key that is to be usedto refer to a service model node that is instantiated by the section ofthe template under consideration. The attributes enclosed within theangled brackets (“<>”) must be one of the attributes of the elements ofthe discovered instance for which there is a reference by the matchcriteria.

The “components” instruction specifies the parent-child relationship ina service model instance. Various types of dependencies (i.e., executiondependencies, component dependencies, inter-service dependencies andorganizational dependencies) are captured by this specification. Thecomponents list specified must make reference to the node in the servicemodel instance 40 that is to be generated from the service modeltemplate 34. The components list refers to specific nodes, all nodes ofa specific type, and all nodes of a different specific type that have aspecific attribute value. Sections of the service model template thatrefer to leaf nodes of the service model instance do not have componentspecifications.

The “measurements” instruction specifies a list of measurements thatmust be targeted at the corresponding node in the service mode instance40. By processing the measurement specifications of nodes in the servicemodel instance, the measurement agent configurator 44 of FIG. 2 candetermine the agents that must be scheduled for execution against eachelement of the discovered instance 36. It should be noted that not allnodes in the service model instance have measurement specifications.

The “StateComputationRule” instruction covers how the states of thecorresponding nodes-in the service model instance 40 are computed. Bydefault, the state of a node in the service model instance is determinedbased on the states of all of the measurements associated with a nodeand the states of all of its dependencies (children nodes) in theservice model instance. The service model creation engine 38 may supportadditional state computation policies. For example, a “measurementsOnly”policy indicates that only the states of the measurements associatedwith a node must be taken into account in determining the state of thatnode.

Regarding attribute value settings, each service model node may deriveattributes from the discovered instance 36 to which it refers. Theservice model template syntax also allows for hierarchical aggregationof attributes. This is demonstrated in the append construct used fordefining category attributes for the service model nodes.

Service Model Creation Engine

The service model creation engine 38 incorporates the logic forprocessing a service model template 34 with the discovered instance 36to generate the service model instance 40. There are alternatives withregard to the order in which the engine 38 processes the service modeltemplate. In a sequential processing approach, it is assumed that theservice model template was constructed such that the sections of theservice model template are in an order in which they need to beprocessed. The engine can then process the sections sequentially. Thesequential processing enables simplification of the service modelcreation engine. However, this approach burdens the template developerwith a requirement of manually determining the placement of each sectionin the template based upon the order of processing. Moreover, sinceprocessing typically starts from the host nodes, this approach mayresult in a number of service model host nodes that do not haveadditional nodes above them when a service model instance graph isgenerated in a manner to be described below. To avoid such “orphaned”nodes, the created service model instance must be further processed.

In the alternative hierarchical processing, a service model creationengine 38 can use the “components” specifications in the differentsections of the service model template 34 to determine the order forprocessing the sections of the template. Since the components listspecifies the dependencies of a node, before processing a section, allof the sections corresponding to each of the nodes types in thecomponents list must be processed. Based on this rule, sections of thetemplates which have no specified components are processed first.Although this hierarchical approach requires more complexity than thesequential approach, it does not result in any orphaned nodes in theservice model instance 40.

Service Model Instance Specification

Table 5 is an example of a portion of a service model instancespecification for the service model template of Table 4 and thediscovered instance of Table 3. The variables of the table areconsistent with the variables of Tables 2-4. Referring now to FIG. 2,the service model instance 40 may be used by the view generator 42 toprovide any of the three views. Preferably, the service model instanceis represented as a graph of the nodes and edges that identifydependencies among the nodes. The service model instance is also used bythe measurement agent configurator. Information from the instance may beextracted by the configurator to merge test information relevant toparticular elements with default algorithm descriptions in order togenerate a measurement agent specification 46 for the ISP of interest.

TABLE 5 [10.174.173.23-fakeisp.net:DNS] ipAddress=10.174.173.23hostName=dns1.fakeisp.net domainName=fakeisp.netcategory=ExternalDnsServer [10.174.173.23:SM-Host]measurements=TCP-Connection-Rate(10.174.173.23), VMstat(10.174.173.23),IFstat (10.174.173.23) ipAddress=10.174.173.23 hostName=dns1.fakeisp.netstate=Alive category= [10.137.196.52:SM-Host]measurements=TCP-Connection-Rate(10.137.196.52), VMstat(10.137.196.52),IFstat (10.137.196.52) ipAddress=10.137.196.52hostName-mailfes21.fakeisp.net state-Alive category=[10.137.196.54:SM-Host] measurements=TCP-Connection-Rate(10.137.196.54),VMstat(10.137.196.54), IFstat(10.137.196.54) ipAddress=10.137.196.54hostName=mailfes22.fakeisp.net state=Alive category=[10.137.196.56:SM-Host] measurements=TCP-Connection-Rate(10.137.196.56),VMstat(10.137.196.56), IFstat(10.137.196.56) ipAddress=10.137.196.56hostName=mailfes23.fakeisp.net state=Alive category=[10.137.196.58:SM-Host] measurements=TCP-Connection-Rate(10.137.196.58),VMstat(10.137.196.58), IFstat(10.137.196.58) ipAddress=10.137.196.58hostName=www.fakeisp.net state=Alive category= [10.137.196.69:SM-Host]measurements=TCP-Connection-Rate(10.137.196.69), VMstat(10.137.196.69),IFstat(10.137.196.69) ipAddress=10.137.196.69hostName=www.xyz.com.fakeisp.net state=Alive category=[10.137.196.70:SM-Host] measurements=TCP-Connection-Rate(10.137.196.70),VMstat(10.137.196.70), IFstat(10.137.196.70) ipAddress=10.137.196.70hostName=www.abc.com.fakeisp.net state=Alive category=

Customizing the Service Model to an ISP'S Organizational Structure

As previously noted, the service model instance 40 of FIG. 3 iscustomized to an ISP's organizational structure, so that ISP operationspersonnel only view the status of services and service elements that areof relevance to the personnel. A straightforward approach to customizingthe service model instance to an ISP's organizational structure is toedit the service model template to explicitly include nodes that capturethe organizational dependencies. For example, the nodes may be groupedaccording to categories (e.g., InternalWeb services and WebHostingservices). Each of these categories may be managed by differentoperations personnel. To accommodate this case, the service modeltemplate could be modified to define nodes that represent the individualcategories and dependencies that indicate the components of thedifferent categories. Since the organizational structure varies from oneISP to another, the approach would require that each ISP edit theservice model templates to match their organizational structure. Editingthe service model template to define the categories and the componentsrelationships can be a tedious task, especially for a large ISP.

An alternative approach is to allow an ISP to specify its organizationalstructure using the configuration interface 60 previously described withreference to FIG. 3. The service model template 34 is pre-specified toexploit the configuration specification and to generate a service modelinstance that is customized to each ISP. The main advantage of thisapproach is that the ISP operator only has to primarily edit theconfiguration specification, which is much less complex than editing theservice model template 34.

The application of this less complex approach can be described withreference to Tables 1-5. Through the configuration interface 60, an ISPoperator specifies ways in which the discovered services and servicemodels are to be categorized in the discovered instance 36. In Table 1,the configuration specification indicates that the ISP uses the namingpattern *.com.fakeisp.net to identify web servers that are hosted forthe businesses. Web servers that do not match this pattern are internalweb servers that are used by the ISP's residential customers. Each ofthe discovery modules 50, 52 and 54 then uses the configurationspecification to determine a categorization of the services and servicemodels that are discovered. A discovery module is also included in thediscovery template 48 to discover and report on all the categories thathave been discovered in the ISP's system. This information is used bythe service model creation engine 38 to construct a service modelinstance 40 that represents the ISP's organizational structure. Toenable this, the service model template of Table 4 has a section thatgenerates a node in the service model instance for each category in thediscovered instance. The components list in this section maps all theservices and service elements that are associated with a category to thecorresponding node in the service model instance. Thus, by merelyspecifying the categorization of services and service elements using theconfiguration specification, an ISP operator can derive a service modelinstance that is customized for the ISP.

Example: Read Mail Service Model

As an example implementation of the system of FIG. 2, the email serviceof “Read Mail” will be considered. The Read Mail service refers to asubscriber accessing his/her mailbox from the mail system of the ISP.FIG. 4 illustrates a service topology for this service. Using a clientapplication that supports the Post Office Protocol-Version 3 (POP3), asubscriber at a desktop computer 62 attempts to access mail. Internal tothe ISP system, the request from the subscriber's computer 62 may bereceived and processed by one of many servers 64, 66 and 68 thatconstitute a mail service group 70. The servers within the group arefront-end servers (FESs).

Before the subscriber can access the appropriate mailbox, the mailserver 64-68 that handles the request contacts an authentication server72 to verify the identity of the subscriber. Typically, passwordidentification is used in the Read Mail service. A subscriber database74 is accessed in this process. Following the authentication process,the mail FES 64-68 accesses a mailbox 78 of the subscriber from aback-end content server 76 using the NFS service. The retrieved mailmessages are transmitted to the computer 62 of the subscriber.

There are several active and passive measurements that can be made toassess the health of the different elements involved in supporting theRead Mail service. A measurement system (MS) may be installed in theserver farm of the ISP to perform measurements using agents executing onthe MS and on the different ISP hosts. The different measurements thatcharacterize the Read Mail service include an active service qualitymeasurement of availability and response time made from the MS in theservice farm, an active measurement of network throughput from the MS inthe service farm to the POP sites, passive measurements of CPU andmemory utilization passive measurements of TCP connection traffic andpacket traffic to the mail servers obtained from agents executing on themail servers, and passive measurements of NFS statistics (e.g., numberof calls, timeouts, and duplicate transmissions) on the mail servers andthe mail content servers. The active measurements attempt to assess theservice quality as viewed from subscribers connecting to the POP sites,while the passive measurements may be used to assess resourceutilization and traffic statistics that are critical for problemdiagnosis.

FIG. 5 is an illustration of an example of a view that may be presentedto an ISP operator using the view generator 42 of FIG. 2. While theoval-shaped nodes in the service model graph represent the differentservices and service elements, the arrows represent measurements ofservices and service elements. The root of the service model graph isthe Read Mail service, represented by oval 80. The state of this noderepresents the overall health of the Read Mail service, as assessed bythe MS located in the service farm of the ISP. That is, the overallhealth is assessed without considering the state of the network linksfrom the server farm to the POP sites. In one embodiment, the overallhealth is represented by color coding the oval 80. For example, oval 80may be shaded green to designate a positive health of the Read Mailservice, and may be shaded red if the Read Mail service has degraded inits availability or performance.

Typically, there is no direct measure of the overall health of the ReadMail service. Instead, the state of the service must be inferred, basedon the states of the different mail FESs 64-68 that together enable theRead Mail service. Direct active measures of availability andperformance, and passive measurements of TCP statistics to the POP3service port, together contribute to the determination of the status ofthe Read Mail service. The active and passive measurements are performedat each of the mail FESs, as indicated by the arrows corresponding tothe second level service oval 82 in FIG. 5.

The next level of the service model graph reflects the dependencies ofthe Read Mail service on one element and two services. Oval 84 is thedependency of the Read Mail service on a POP3 server executing on themail FES. Oval 86 represents the authentication service for verifyingthe identity of the subscriber from which a Read Mail request isreceived. Oval 88 represents the NFS service used by the particular mailFES. Considering the POP3 server 84 first, the health of the server ismeasured based on the ability to establish a TCP connection as part ofthe active Read Mail service quality measurement and the time requiredto establish the connection. In turn, the health of the POP3 server maybe impacted by the link, represented by oval 90, interconnecting themail FES to the measurement station (from which the active test is run)and the health of the mail FES host, represented by oval 92. As shown inFIG. 5, both the link 90 and the host 92 include four performanceparameters that are measurable in determining the health of the nodes.While not shown in FIG. 5, the state of the various nodes may berepresented by color coding or by other display means for distinguishingthe states of the nodes.

Regarding the dependency of the authentication service 86 on the mailservice 82, since it is possible that the authentication service ishealthy but a specific mail FES is failing to perform authentication,the authentication service is first represented from the point of viewof each of the mail FESs 94. Direct measures of the authentication delaywhen accessing through a mail FES are used to determine the state of themail authentication service 86 in relation to that mail FES 94. Theservice model for an authentication service node, whose state affectsthe state of the mail FES-specific authentication node, is not expandedin the service model graph of FIG. 5. Likewise, the NFS service 88 isnot shown as being expanded in the service model graph. The servicemodel dependency is handled in much the same way as the authenticationservice dependency.

As previously noted, the service model graph of FIG. 5 represents theRead Mail service in isolation. To represent the end-to-end service, aservice model must take into account the state of the DNS service usedby subscribers to resolve the ISP mail domain to each one of the mailFESs, and the state of the network links between the different POP sitesand the ISP server farm. Clearly, since the different POP sites usedifferent routes to connect to the service farm, a subscriber'sperception of the end-to-end service may vary, depending upon the POPsite that the subscriber is using. FIG. 6 is a service model graph forthe Read Mail service as perceived by a subscriber connected to the ISPsystem via POP_(m). The Read Mail POP_(m) service is represented by oval96 and has the Read Mail service 80 of FIG. 5 as one of itsdependencies. However, the service 80 is not expanded. While not shownin FIG. 6, the graphing preferably includes color coding or otherdesignation for nodes, such as the service 80, which are not fullyexpanded.

The other dependencies on the Read Mail POP_(m) service 96 include thelink 98 and the DNS service 100. The health of the link is determined bymeasurements of the performance parameters throughput, packet loss,delay and connectivity. The health of the DNS service 100 is determinedby measurements of availability and performance. The DNS service 100 isshown as having the dependency POP_(m) DNS server 102. In turn, theserver 102 has two dependencies, namely POP_(m) DNS host 104 and thelink 106.

There are several ISP management functions that can exploit thecapabilities of the service models. For example, a service model foroperational monitoring may be configured to indicate the status of thedifferent elements providing a service. When a failure occurs, theservice model indicates which element or elements have been affected bythe failure. More-over, by traversing the service model graph top-down,an operator can determine the root-cause of the failure. For example, inFIG. 5, when a problem is noticed with the overall Read Mail service 80,an operator can traverse the service model graph to determine whetherthe problem is caused by a specific mail FES or whether all of the mailFESs are experiencing a problem. Assuming a similar scenario, movingdown the service model graph, the operator can further determine whetherthe problem is related to authentication failure, NFS failure, or afailure of the POP application server 84.

Since services and service elements can be organized based on domains ofresponsibility in a service model, ISP operations personnel need onlymonitor and diagnose the services that fall in their domain ofresponsibility. In the Read Mail service example of FIG. 4, an emailoperations expert who is responsible for the mail service and the mailservers uses the service model depicted in FIG. 5, since the expert ismainly interested in the states of the email services and servers. Theauthentication and NFS services are included in the service modelrepresentation, since these services can adversely impact the Read Mailservice. In contrast, the links between the service farm and the POPsites are not included in the model, since they do not affect the ReadMail service from the perspective of the email expert.

Measurement Topology and State Representation

As can be seen in FIGS. 5 and 6, the service model maps differentmeasurements for some of the nodes in the service model graphs. The nodeto which a measurement maps depends on the semantics of the measurement(i.e., which logic node or nodes are targeted by the measurement) andthe location or locations from which the measurement is made. In thesimplest case, each measurement directly maps to one of the nodes in theservice model. In some cases, measurements may span multiple services orservice elements and there may not be a direct mapping of a measurementto a node in the service model. In such cases, composite measurements,which are combinations of measurements being made in the ISP system, mayhave to be composed and mapped to the nodes in the service model. Forexample, suppose Link (x,y) is a network link interconnecting hosts xand y in an ISP system, and suppose Link (x,y) is comprised of Link(x,z) and Link (z,y). If measurements are made from x, Link (x,y) andLink (x,z) can be directly measured. The status of Link (z,y) has to bederived from the status of Link (x,y) and Link (x,z).

Each of the nodes in the service model has an instantaneous stateassociated with it. As previously noted, the state of a node reflectsthe health of the service or service element that it represents. Anumber of policies can be used to compute the state of service modelnodes. One policy computes the state of a node based on all of itsmeasurements. Another policy assigns weights to the differentmeasurements based on an estimate of their reliability, as gauged by adomain expert. Yet another policy determines the state of a node basedon its measurements in combination with the states of its dependenciesin the service model graph. The states of the measurements associatedwith a node may be determined by applying baselining and thresholdingtechniques to the measurement results.

Discovery Methodologies

Returning to FIG. 3, the preferred embodiment of the management system56 includes a discovery engine 58 that automatically discovers services,service elements and dependencies among services and service elements.While the invention may be utilized in an environment in which thediscovered instance 36 is input manually, auto-discovery is preferred.FIGS. 7 and 8 illustrate applicable discovery methodologies. Similar toexisting management system implementations, a first phase of discoveryis performed from a management station 108, which may be external to theservice farm of the ISP system. Predominantly, this phase involvesactive tests that generate test traffic and query all of the ISP hoststo detect the existence of different types of servers 12, 14, 22, 26 and28. That is, the phase detects execution dependencies, as defined above.Component and organizational dependencies are also detected during thisphase. Moreover, some of the inter-service dependencies are discovered,but the second phase is focused on the inter-service dependencies, sinceit may not be possible to discover all the inter-service dependenciesthat exist using tests executed from outside the ISP host. The secondphase uses an internal view of the ISP system. Preferably, the twophases are executed sequentially, with the second phase utilizing thediscovered information output by the first phase to direct itsoperations. Different mechanisms can be employed in the internaldiscovery phase. Both phases of discovery must be executed periodically,so as to discover new services and service elements that may have beenintroduced into the ISP environment.

In FIG. 7, a single discovery agent 110 is used in the first phaseexternal discovery process. The solid line 112 represents the discoveryagent contacting the DNS server 14 to get a list of hosts in the ISPsystem. The dashed lines from the discovery agent 110 indicate activetests being executed by the discovery agent to detect various types ofdependencies that exist.

FIG. 8 is an illustration of the second phase internal discoveryprocess. In this phase, a number of internal discovery agents 114, 116,118 and 120 are utilized. The solid lines having arrows at one endindicate the discovery of inter-service dependencies. The dashed linesindicate the flow of discovered instance information back to themanagement station 108.

Both phases of the discovery process may employ one or more differentbasic categories of discovery techniques. Under the service-independenttechniques, hosts and networking equipment (routers 20, hubs 18, and POPsites 16) which are not specific to any service are discovered. As asecond category, using service-generic techniques (which may be the sametechniques, but with appropriate parameterization for each service) maybe used to discover instances of different services. In order to do so,typically, such discovery techniques exploit common characteristics ofdifferent services to discover instances of the services. An example ofthis second category is a discovery technique for News, Web and emailservices. Since all of these services rely upon the same transportprotocol (i.e, TCP), a discovery technique can discover the existence ofapplication servers by connecting to the TCP ports corresponding to theservices.

Another category of techniques may be referred to as theservice-specific-but-application-independent techniques. Techniques inthis category are specific to the service. They are intended to monitor,but may be used for discovery that is independent of the specificapplication server that is being used to implement the service. Forexample, the discovery of the relationship between the services offeredby POP3 email servers and the service provided by SMTP-based emailservers is possible using application-independent techniques, since therelationship is accessible from the domain name service in the form ofmail exchange (MX) records.

A fourth category may be referred to as application-specific techniques.Many inter-service dependencies may need to be discovered in a mannerthat is very specific to the application servers providing the services.For example, to discover the dependency of the web service on NFS, thediscovery technique may have to query the configuration file in the webapplication server that is providing the web service. Since the formatand contents of a web application server's configuration file isspecific to the application, the discovery technique isapplication-specific.

First Phase External Discovery

An often under utilized component of an ISP system is the domain nameservice (DNS). In order to allow subscribers to access hosts using theirhost names, rather than their more difficult to remember IP addresses,DNS stores the host name-to-IP address mapping for all of the hosts inthe ISP system. Moreover, the exchange of email messages across hostsoccurs using the mail exchange records maintained by the DNS. Nameserver (NS) records in the DNS database serve to identify authoritativename service for the ISP domain—these are name servers that areexternally accessible from the global Internet and are the authoritiesthat are contacted when users in the global Internet attempt to accessany hosts in the ISP system. Moreover, service groups, such as an emailservice group, are enabled via round-robin scheduling mechanismsimplemented in the DNS servers. In summary, the domain name system holdsa wealth of information that is critical for auto-discovery of ISPservices. However, additional mechanisms are necessary to complementDNS-based discovery mechanisms.

One of the first steps in discovery is to determine all of the hoststhat exist in the ISP system. Most existing network management systemshave taken one of two approaches. A first approach is to scan an addressrange that is either specified by an operator or is determined based onthe local subnet of the measurement host. The address range is scannedusing ping to solicit responses from all IP-enabled hosts. The secondapproach is to use the default router configured for a host toboot-strap the discovery. Communication using SNMP with the router andusing its routing tables may be used to discover hosts in the localsubnet. Also, routing table information may be used to discover otherrouters that can provide additional host information.

An alternative approach that is complementary to either of the twotraditional approaches is to obtain a list of all of the hosts in theISP system using information available with the domain name service.From the host name of the management station in which the discoveryprocess executes, the ISP domain name can be deduced. Using the defaultname service configured for the management system, the discovery processqueries DNS to obtain the NS records that list the authoritative nameservers for the ISP domain. One or more of these name servers arecontacted by the discovery process to obtain a list of named hosts inthe ISP system. Zone transfer capabilities supported by all DNS serversare used for this purpose, as is known in the art. While ISPs usuallymanage a single domain, some ISPs may have multiple domains under theircontrol. To discover all of the hosts that exist in the differentdomains, the discovery process must be informed of the existence of allthe different domain names. This information cannot be automaticallydeduced by the discovery process.

The steps that are executed in the first phase of discovery areidentified in FIG. 9. It is not critical that the steps be followed inthe order shown in the figure. Following the step 122 of discovering thehosts, the application servers are discovered in step 124. The existenceof application servers of different types (e.g., Web, email, News, FTP,DNS, NFS, and Radius) is verified by active tests that emulate typicalclient requests directed at the different TCP and UDP portscorresponding to the different service types. A response to an emulatedrequest has to be interpreted in a service-specific manner. By observingthe header in a response from the web service, the discovery processdetermines the type of web server that is executing on the host machine.Likewise, by processing the response returned by the email and Newsservers, the discovery process determines the type of servers. Thisinformation can be used to customize the second phase of discovery. Forinstance, discovery agents installed on the ISP host machines in thesecond phase of discovery may process a web application server'sconfiguration files to discover NFS dependencies that the server mayhave. Since web server configuration files are typically specific to thetype of server, the server type information provided by the first phaseof discovery can be used to determine the processing capabilities of thediscovery agent or agents that must be deployed in the second phase. Theserver type information may also be used to determine specificmeasurements which must be targeted for the server to monitor itsstatus.

In step 126, the existence of Web, email, News, DNS and other servicegroups has to be determined using the DNS. By querying the DNS, thediscovery process determines a list of domain names that have multipleIP addresses associated with them. For each name in the list, thediscovery process then determines whether each of its IP addresses hostsa common application server. If so, the name likely represents a DNSround-robin service group that supports a common service. For example,suppose that all of the IP addresses corresponding to the namewww.fakeisp.net host web servers. In this case, www.fakeisp.netrepresents a web service group. Note that in this process, a host thathas two network interfaces, and therefore is assigned to different IPaddresses, may be listed as a service group. Using the virtualhost/server discovery heuristics discussed below, all such hosts can beremoved from the service group list.

In step 128, the MX records for the ISP domain are accessed from the DNSsystem. The MX records indicate the mail servers that must be contactedto deliver mail to the ISP domain. The list of SMTP-based mail serversthus determined represent the servers that handle delivery of incomingmail to the subscribers of the ISP. Discovery of these servers isessential to automatically generating a service model for the emailservice that represents the delivery of mail from the Internet to thesubscribers. Moreover, the mail gateways may be managed by a differententity than the one that manages mail servers that are internal to theISP.

One of the critical measures of the performance of an email service ofan ISP is the round-trip delay between the transmission of an emailmessage from a source host and its reception at the intendeddestination. This measurement can be used to assess email delivery timesin the ISP domain, from the ISP domain to locations on the Internet, andfrom locations on the Internet to the ISP domain. Since the emailservice uses different protocols and hence, different applicationservers to send mail and to receive mail, in order to initiateround-trip delay measurements of email, it is essential to determinerelationships between the different types of email servers on the ISPdomain (e.g., which SMTP server can be used to send mail to aPOP3/IMAP-based server). This discovery is executed at step 130. Sincemail forwarding is predominantly based on the MX records maintained inthe DNS database, by querying the DNS system for MX recordscorresponding to each of the POP3/IMAP servers, the discovery processdetermines the mail service relationships in the ISP domain.

Various approaches can be adopted to discover the terminal servers thatexist in an ISP POP site in step 132. The most straightforward approachuses SNMP queries to obtain the MIB-II system description from all thehosts in the ISP network. Based on the replies, the discovery processcan identify the hosts that are terminal servers. An alternativeapproach is based on the observation that because they need to operateand manage thousands of terminal servers, most ISPs have specific namingconventions that they use when naming their terminal servers. In fact,the naming convention more often indicates the association betweenterminal servers and POP sites, so that when a problem is reported by asubscriber using a POP site, the ISP operations staff can quickly decidewhich of the terminal servers needs to be checked in order to diagnosethe problem. With this approach, an ISP provides a regular expressionrepresenting the naming convention used as input to the discoveryprocess. By matching the list of hosts that are discovered with thenaming convention, the discovery process not only determines theterminal servers that exist, but also determines the POP site to which aterminal server is assigned. Another key advantage of this approach isthat it performs discovery without generating any additional networktraffic.

The approach of exploiting name conventions may also be used in step 134to categorize the other services of the ISP. As an example, for each website that it hosts for its business customers, a particular ISP mayassign internal names of the form *.com.fakeisp.net, so that a hostedweb site named www.customer-domain.com will have a corresponding entryfor www.customer-domain.com.fakeisp.net in the internal DNS database ofthe ISP. As in the case of terminal servers, by permitting an ISP tospecify its naming conventions, the discovery process composes acategorization of services that is customized to the target ISP system.This categorization can be based on geographical locations of services,based on business relationships, and/or based on the delegation ofresponsibilities among operators. The categorization information can beused to automatically define the customized service model for each ISP,with special nodes in the service model representing a collection ofnodes pertaining to the same category.

Second Phase Internal Discovery

By treating the ISP system as a “black box,” the first phase of externaldiscovery detects most of the execution, component and organizationaldependencies of the ISP. Additionally, some of the inter-servicedependencies are discovered. The internal discovery process is focusedsolely on detecting inter-service dependencies, particularly those thatare not discovered by taking an external viewpoint. For example, therelationship between a mail server and an NFS server is not discoverablefrom an external viewpoint.

There are two basic approaches for conducting the internal discovery.One approach uses network probes, while the other approach usesspecial-purpose discovery agents. Regarding the first approach,soft-ware probes installed at strategic locations on the network cansnoop on packet transmissions. Since most TCP/IP communication is basedon source/destiny port numbers, by processing the headers of packetsthat are captured by the probe, a software probe can deduce many of therelationships that exist among services. For example, a UDP packettransmitted from a mail server to the NFS port of an NFS serverindicates that the mail server depends on the NFS server for its contentstorage.

An advantage of the approach that utilizes network probes is that theapproach enables discovery of inter-service dependencies independent ofthe specific types of application servers residing on the host.Moreover, since it relies on just the ability to capture packets on thewire, this approach handles UDP and TCP-based services equally well.

The key difference between the approach of using network probes and theapproach of using special-purpose discovery agents is that unlike thenetwork probes, the discovery agents do not snoop on packettransmissions. Instead, the discovery agents use a number of operatingsystems and application-specific mechanisms to discover inter-servicedependencies. These mechanisms include (1) processing serviceconfiguration information and (2) application-dependent monitoringtools. Referring first to the processing service configurationinformation, application servers determine their dependencies on otherservices from one or more configuration files. By processing the contentof the configuration files, discovery agents can discover inter-servicedependencies. An example of this is the processing of the web server'sconfiguration file to discover whether it has a dependency on an NFSservice. While processing the web server's configuration file, thediscovery agent can also determine if the same application is being usedto host multiple “virtual” servers (which is commonly used by ISPs tohost web sites on behalf of their business customers). Typically, webserver configuration files are specific to the type of server executedon the web server in use. The server type determination performed duringexternal discovery (i.e., the first phase of discovery) is used fordeciding the location and format of the configuration files.

While many Unix operating systems use configuration files that aredefined in an application-specific manner, Windows NT-based systemsstore all application configuration information in the registry. In theWindows NT systems, while the registry can be processed in anapplication-independent manner, the specific configuration attributeshave to be interpreted in an application-specific manner.

Thus far, only forward-looking discovery agents have been identified.These are agents that discover dependencies of a service on otherservices by querying configuration files of the application providingthe service. Sometimes it is easier to implement backward-lookingdiscovery agents to discover the dependencies on a service (i.e.,discover which other services are using the service). For example, theconfiguration file of the mail authentication server may indicate whichof the mail servers are depending on the authentication server. One ofthe ways of implementing backward-looking discovery agents is byprocessing application server configuration files.

Turning now to the second mechanism of using application-independentmonitoring tools, this approach is particularly attractive for servicesthat communicate using TCP. The netstat utility can be used to determinethe TCP connections that exist on an ISP host. A discovery agent thatexecutes this tool can periodically discover information about thesource and destination ports and the host locations for TCP connections,which can then be used to deduce inter-service dependencies.

This second approach of using application-independent monitoring toolsexploits the fact that most TCP implementations enforce a three-minutedelay for connections in the TIME_WAIT state of TCP, so that aconnection persists for about three minutes even after it is no longerin use. Consequently, whenever the discovery agent is executed, it islikely to detect all the TCP connections that may have been establishedin the three minutes prior its execution. This same approach does notwork for UDP-based services, since UDP is connectionless, and there isno state that is maintained at either the source or the destination.

The approach of monitoring TCP connections can be used to discoverdependencies such as those that exist between mail servers and mailauthentication servers, between servers and back-end databases, betweenRadius/TACACS authentication servers and terminal servers, and betweensimilar relationships. Again, discovery agents can be forward-looking orbackward-looking.

Advantages of using discovery agents, as compared to network probes,include the reduction of overhead on the ISP hosts, the relaxation ofsecurity concerns, and the fact that all of the discovery agents do notneed to be deployed at the same time. Instead, the deployment ofdiscovery agents can occur at the discretion of the ISP. As and when newdiscovery agents are installed on the ISP hosts, additional informationis discovered about the ISP system.

FIG. 10 is a process flow of steps relevant to the second phase of thediscovery process. In steps 136 and 137, the information that isobtained in the first phase of discovery is used to generate anincomplete service model instance. As previously noted, the first phaseof discovery provides the necessary information for identifyingcomponent dependencies, organizational dependencies, executiondependencies and some of the inter-service dependencies. A firstinstance generator matches the service model template with theauto-discovered information from the first phase to generate theincomplete service model instance. However, other inter-servicedependencies are not discoverable using the techniques of the firstphase (e.g., the relationship between a mail server and an NFS server).

In steps 138 and 139, the holes in the incomplete service model instanceare identified and information obtained in the first phase is used todetermine appropriate discovery actions. The incomplete service modelinstance is used to determine the types of relationships that must beexamined. In the mail service example, if a host is discovered in thefirst phase to be running a POP3 server, the second phase may be used todiscover the network file service and authentication service used by thePOP3 server on the particular host.

In step 140, the network probes and/or the special-purpose discoveryagents are deployed in a manner determined during execution of the step139. For example, application-specific knowledge may be used to parseconfiguration files or log files, or may be used to search aconfiguration registry for a particular server instance executing on aparticular host. The network probes and/or discovery agents generateservice dependency outputs in step 141. The outputs are used in a secondinstance generation to complete the service model instance in step 143.

Extensible Discovery Architecture

Since new network services and service elements are being deployed at arapid pace, it is important that the discovery methodologies beimplemented in an extensible manner, allowing new discovery capabilitiesto be incrementally added to the management system. FIG. 11 depicts theextensible architecture for discovery components previously describedwith reference to FIG. 3. The discovery modules 50, 52 and 54 representthe logic used for discovery of different services and service elements.The discovery template 48 is the key to the extensibility of theauto-discovery architecture in the sense that it drives how discovery isperformed. The template defines the different services and serviceelements that need to be discovered, and the specific discovery modulesthat can be used to discover these elements. The template alsoestablishes the format of the outputs from the modules.

The discovery engine 58 drives the auto-discovery process. The discoveryengine interprets the discovery template 48 and for each of the serviceor service element types specified in the template, the engine invokesthe corresponding discovery module 50, 52 and 54 specified in thetemplate. All of the discovery modules report the results of theirexecution back to the discovery engine. The discovery template containsinstructions for the discovery engine to process the output of thediscovery modules and to record them as a discovered instance 36.

Some discovery modules may rely on the discovery results of otherdiscovery modules. For example, a DNS round-robin service groupdiscovery module for web services relies on identifying which hostssupport web services, which is an output of the web service discoverymodule 50. To accommodate these relationships, as part of the interfacethat the discovery engine 58 exposes to the discovery modules, theengine provides ways for accessing and searching the instancesdiscovered by other discovery modules.

In contrast to the discovery modules 50, 52 and 54, the discovery engine58 is designed to be independent of the services that need to bediscovered. Consequently, to discover new services or service elements,a user merely has to provide a discovery template specification or oneor more discovery modules for each new element. By providing analternate discovery module for a service that is already supported, auser can also enhance capabilities of an existing discovery system.

In practice, there are two significantly different approaches todesigning the discovery engine 58 and the discovery modules 50-54. Afirst approach is to enable the discovery engine to control thediscovery process. The discovery engine accesses the discovery templateand determines the order in which sections of the template areprocessed. On the other hand, in the second approach, the discoverymodules drive the discovery process. In effect, this is an event-drivenapproach, since the results obtained from one module will triggersubsequent activities by other modules.

Regarding the first approach in which the discovery process is driven bythe discovery engine 58, FIG. 12 illustrates the logical building blocksof the discovery engine. The discovery engine executes periodically andeach time it starts, the engine processes the discovery template.

By considering the values of the dependencies variable for each of thesections in the discovery template, the discovery engine determines theorder in which the sections must be processed. Thus, the discoveryengine includes a template parser 142. Sections of the template whichhave no dependencies are processed first. A module loader 144 directsthe relevant information to the appropriate discovery module 146 forprocessing a particular section in which no dependencies are identified.After all such sections are processed, the discovery engine iteratesthrough the list of template sections, choosing sections which have notbeen processed and which have their dependencies determined by earlierprocessing. This process is repeated periodically to discover newinstances as and when they are added to the system being discovered. Inone application, the discovery engine uses the exec system call toinvoke the discovery modules as separate processes. By doing so, thediscovery engine is able to handle discovery modules written in avariety programming environments.

A query processor 148 of the discovery engine 58 performs two functions.First, when a module 146 is activated, the processor 148 queries thediscovery engine to obtain configuration information that guides thediscovery modules. In FIG. 3, the configuration information is generatedfrom the configuration interface 60 that is manipulable by a user. Table1 was previously included to depict a typical configuration file. Eachline in the file represents an instruction for one of the discoverymodules. The first column of the line identifies the discovery module towhich the instruction pertains. There are three types of instructionsthat are specified in the configuration file. All of these instructionsspecify regular expression patterns that must be applied against the IPaddress or host name of the service or service element. The instructionsin the configuration file are (1) criteria that instruct the discoverymodules to include or exclude specific services or service elements, (2)criteria that instruct the discovery modules to associate specificservices or service elements with certain categories, and (3) criteriafor discovering terminal servers and for extracting POP site-to-terminalserver mapping from the terminal server names.

The second function of the query processor 148 is to provide thediscovery modules 146 with access to previously discovered instances.Based on configuration and discovered instance information obtained fromthe query processor, the discovery modules perform tests on the ISPsystem and report their discovery output to the discovery engine. Adiscovery instance generator module 150 of the discovery engineprocesses the results of the discovery modules and outputs the discoveryinstance in an appropriate format. An example of such a format waspreviously set forth in Table 3. The formats of the discovery templateand the discovery instance are thereby hidden from the discoverymodules.

As previously noted, the second approach to designing the discoveryengine 58 and the discovery modules 50-54 of FIG. 11 is to establish anarrangement in which the discovery process is driven by the modules. Inthis alternative embodiment, the discovery engine processes the templateonce, invoking the discovery modules simultaneously. From this point,the discovery modules determine when different elements in the ISPsystem are discovered. The discovery modules execute periodically,looking for new instances. Some discovery modules are independent in thesense that they are not reliant on other modules for discovery. Theseindependent modules begin executing immediately.

As and when a discovery module 50-54 discovers a new instance, thediscovery module forwards its results to the discovery engine 58. Basedon the dependencies on a discovery module, as specified in the discoverytemplate 48, the engine 58 forwards the results to other discoverymodules for which the results are relevant. The availability of newresults (e.g., the discovery of a new host) may trigger discovery byother modules (e.g., the web server module checks to determine if a webserver is executing on the new host), and this process continues. A keyadvantage to this approach, as compared to the engine-driven discoveryapproach, is that multiple discovery modules may be executing inparallel, discovering the ISP's services. In this approach, thediscovery engine 58 mainly functions as a facilitator of communicationamong the discovery modules. A variant of this approach may not eveninvolve the discovery engine, with the discovery modules registeringinterest in other discovery modules and information concerning newlydiscovered instances being directly communicated among the discoverymodules, without involving a discovery engine.

Integrating Discovery with Service Models

In the scenario in which the management system uses service models formanagement of Internet services, there are two ways in which discoverycan be integrated with service models. In a looser integration, theoutput of discovery is integrated with a service model template thatoutlines the structure of a service, and the integration automaticallygenerates a service model instance that is customized for the ISP systembeing managed. However, the preferred integration is one that provides atighter integration and involves driving auto-discovery and servicemodel instantiation from a common template. In this preferred approach,for each node in the service model, corresponding discovery templatespecifications are provided. The discovery and service model-specificcomponents of the template can either be processed in a singleapplication or can be processed separately. This approach towardstighter integration of discovery and service model templates isattractive for several reasons. Firstly, the service model template canserve to constrain the discovery process, since only services andservice elements that are specified in the service model template needto be discovered. Secondly, depending upon its design, the service modeltemplate could end up using some of the outputs of the discoveryprocess. Using a common template permits tighter syntax checking acrossthe discovery and service model components of a template. Thirdly, thetwo-phase approach to discovery described above fits in well with theservice model concept. The inter-service dependencies that need to bediscovered in the second phase (internal discovery) can be determinedbased on the service model template. Finally, the discovery processitself can be determined based on the service model templatespecification. The discovery process may attempt to traverse the servicemodel template tree from a root node down. At each level, it attempts todiscover all services or service elements of the type specified by thenode, providing all of the children of a node have been discovered. Ifthis is not the case, the discovery process proceeds to first discoverall instances of the children nodes. Continuing the tree traversalrecursively, the discovery process discovers all instances that arenecessary to build the service model for the ISP system being managed.

What is claimed is:
 1. A method of modeling services that are availablevia a network comprising steps of: selecting a core service of interest;forming a service model template for said core service such that saidservice model template anticipates possible instances of networkelements and possible instances of network services that cooperate inexecution of said core service, including defining specificationsrelating to linking a plurality of said anticipated network elements andnetwork services; discovering instance information specific to instancesof actual network elements and instances of actual network services ofsaid network; and generating a service model instance of said coreservice based upon a combination of said service model template and saidinstance information, including identifying dependencies among saidactual network elements and actual network services.
 2. The method ofclaim 1 wherein said step of forming said service model templateincludes associating measurable performance parameters with at leastsome of said anticipated network elements and network services, andwherein said step of discovering said instance information includesdetermining measurements for said measurable performance parameters. 3.The method of claim 2 wherein said step of generating said service modelinstance includes indicating state computation rules of said at leastsome actual network elements and network services based on saidmeasurements, said state computation rules being used to compute statesthat are being indicative of performance conditions of said at leastsome anticipated network elements and network services.
 4. The method ofclaim 1 wherein said step of generating said service model instance isexecuted in computer software and includes accessing at least one memorystore in which said service model template and said instance informationare stored.
 5. The method of claim 1 wherein said step of forming saidservice model template includes identifying types of network elements,including servers and connectivity devices, said step of generating aservice model instance including identifying operational links amongsaid actual network elements and network services based upon informationformed within said service model template.
 6. The method of claim 1further comprising forming a discovery template for use as aspecification for executing said step of discovering instanceinformation, said discovery template including instructions fordiscovering said anticipated network elements and network services. 7.The method of claim 6 wherein said step of discovering said instanceinformation is executed in computer software and is partially based onsaid discovery template.
 8. The method of claim 1 further comprisinggenerating a graph of inter-connected nodes in accordance with saidservice model instance, each node representing one of said actualnetwork elements and actual network services.
 9. The method of claim 1wherein said step of forming said service model template is executedwith respect to availability of said core service via one of an Intranetor Internet Service Provider (ISP), said service model template beingsubstantially generic to ISPs, said service model instance beingspecific to said ISP.
 10. The method of claim 1 wherein said step ofidentifying dependencies among said actual network elements and servicesincludes providing indications of dependencies that includeinter-service dependencies, execution dependencies, componentdependencies and organization dependencies.
 11. A system for modeling aselected service that is available via a network comprising: means forstoring a service model template having information regarding possibleinstances of network elements and possible instances of services ascooperating to enable said selected service, said service model templatebeing configured to anticipate multiple said possible instances of saidnetwork elements and services; discovery engine means for initiatingoperations specific to identifying actually discovered network elementsand services, said discovery engine means having an output of instanceinformation specific to said discovered network elements and services;and model creation engine means, connected to access said service modeltemplate and said instance information, for mapping said discoverednetwork elements and services into a framework identified in saidservice model template.
 12. The system of claim 11 further comprisingdiscovery modules controlled by said discovery engine means andconnected to said discovered network elements for acquiring saidinstance information.
 13. The system of claim 12 further comprisingmeans for storing a discovery template having data specific tocontrolling said discovery modules, including data relating toanticipated relationships between discovery modules and network elementsand services and further including data relating to relationships amongdiscovery modules.
 14. The system of claim 12 further comprisinginterface means, connected to said discovery engine means, for enablinguser configurations of execution of said operations initiated by saiddiscovery engine means, thereby enabling selective reconfiguration ofsaid mapping of said discovered network elements and services.
 15. Thesystem of claim 11 wherein said model creation engine means is primarilycomputer software.